LMWHs are being used with greater frequency to treat deep vein thrombosis, unstable angina, and acute pulmonary embolism, as well as thromboprophylaxis agents in a wide range of clinical situations including orthopedic surgery, high risk pregnancy, and cancer therapy. The most common complication of anticoagulation with LMWHs is hemorrhage. Many published clinical studies report 1% to 4% major (life-threatening) bleeding associated with LMWH therapy and there is a 5-fold increase in the overall death rate for acute coronary syndrome patients receiving anti- coagulant therapy that experience major bleeding. Although protamine is commonly used to neutralize UFH following coronary bypass surgery, it is unable to completely reverse the anticoagulant effects of LMWHs or fondaparinux. Therefore, there is a strong medical need for the development of a safe and effective antagonist for the LMWHs. The goal would be to develop an antidote that could rapidly reverse unwanted bleeding yet permit rapid resumption of anticoagulation therapy with a new dose of LMWH to restore thromboprophylaxis. We are developing series of non-peptidic oligomers with well-defined secondary or tertiary structures to serve as novel templates for the design of compounds targeting specific protein- protein and protein-membrane interactions. These oligomers have many advantages over peptides: relatively smaller size which increases stability and enhances tissue distribution, ease of synthesis, resistance to proteolytic degradation, and suitability for medicinal chemistry approaches to fine-tune their physical properties and optimize potency and safety. We have utilized this strategy to design small oligomers that strongly interact with UFH and LMWH and antagonize their anti-coagulation properties. We propose to evaluate the suitability of current lead compounds as antagonists to LMWH and fondaparinux in preclinical efficacy and safety studies designed to identify clinical candidates. In addition, we propose to continue medicinal chemistry efforts in the salicylamide series and a newer series of arylamides to identify back-up compounds to substitute into the discovery program if problems are encountered with the current lead compounds. PUBLIC HEALTH RELEVANCE: Low molecular weight heparins (LMWHs) and the pentasaccharide, fondaparinux, are widely used anti-coagulants employed in a number of clinical and surgical applications. Bleeding complications are common adverse events associated with anti-coagulant therapy. Protamine is an effective antagonist of UFH but presently there are no effective antagonists for the pentasaccharide or the low molecular weight heparins. We are developing safe and effective non-peptidic oligomers to neutralize the anti-coagulation properties of LMWH and fondaparinux.